I was exploring a woodland mansion with a friend and i saw a vindicator, so i put my shield up and then after 1 hit the shield made the breaking noise, but my shield was no where close to breaking and it wasn't broken. After the first hit, every time the vindicator hit me i took damage. I noticed it only happens with vindicators so far because i tested it on some other mobs but the shield still worked after 1 hit. My friend died to one because of this glitch earlier then i just died as well.

*edit 
it’s the axe, i tried hitting my friend with my axe when they had their shield up, then the shield made the breaking noise and even though they didnt do anything the shield went to the side but they still remained crouching and the next hits did them damage

in the video you can see my character in the top corner crouched with the shield on then after it hits me the shield comes off even though i didnt do anything and it makes the breaking noise.